1. Field
The present disclosure relates generally to electronics, and more specifically, to a transconductance cell with good tuning range.
2. Background
Filters are used extensively today in almost every electronic application. A filter is an electrical network that alters the amplitude and/or phase characteristics of a signal with respect to frequency. Thus, a filter may be used in an electronic circuit to emphasize signals in certain frequency ranges and reject signals in other frequency ranges. The behavior of a filter may be described mathematically in the frequency-domain in terms of its transfer function. The transfer function describes the effect of the filter on the amplitude of the input signal at various frequencies.
A transconductance cell (Gm-cell) is often used as a basic building block in filter design, such as low-pass filters. A low-pass filter passes low frequency signals, and rejects signals at frequencies above the filter's pole frequency. The filter's pole frequency is equal to the frequency at which the signal output drops 3 dB below the center frequency. The range of frequencies below the pole frequency is known as the filter's passband. An ideal low-pass filter has a transfer function with a flat response over its passband. However, in actual implementation, the low-pass filter may experience signal distortions in its passband due to the nonlinearity of the Gm-cell. Accordingly, there is a continuing need in the art for Gm-cells with improved linearity for low-pass filter design.